1. Field of the Invention
The present invention relates generally to high-temperature, low dielectric polyimides. It relates particularly to aromatic polyimides which contain 1,3-bis(3,4-dicarboxyphenoxy)benzene in the dianhydride portion and 2,2-bis[4(3-aminophenoxy)phenyl]hexafluoropropane as the diamine portion of the polymer structure.
2. Description of the Related Art
High performance film and coating materials are being used increasingly by the electronic circuit industry. As cited by Senturia (Proc. of ACS Polym. Matls. Sci. and Eng., Vol. 55, 385, 1986), there are four primary applications in the area of microelectronics: (1) as fabrication aids such as photoresists, planarization layers, and ion implant masks; (2) as passivant overcoats and interlevel insulators; (3) as adhesives, and (4) as substrate components. Of utmost importance for the performance of a polymer used for electronic applications is its electrical behavior. To be useful, particularly as a passivant or protective overcoat, the material must be an excellent insulator.
U.S. Pat. No. 4,111,906 (Jones et al.) is directed to a novel aromatic diamine and the use of this diamine in the preparation of polymeric materials including polyimides. However, this reference is not concerned with the preparation of polymers having low dielectric constants.
U.S. Pat. No. 4,645,824 (Landis et al.) is directed to a solvent polycondensation process for preparing high molecular weight polyimides from dianhydrides and diamines. However, this reference is not concerned with the preparation of polymers having low dielectric constants.
Great Britain 1,062,435 is directed to the preparation of polyimides which are useful in the preparation of shaped structures such as films, fibers, filaments, foams, and the like. Like Jones and Landis discussed above, this references does not even mention the dielectric constant of the polyimides produced.
The dielectric constant of commercially available polyimides presently used as state-of-the-art materials for passivants and interlevel dielectrics ranges from approximately 3.2 to 4.0 (depending on frequency and moisture content). The lower limit of 3.2 is obtained on commercial polyimide film, DuPont Kapton.RTM. H film, only after being fully desiccated. Unfortunately, as the film or coating absorbs moisture, the dielectric constant rises, making measurements and operation of electronic devices complicated.
Accordingly, a primary object of the present invention is to provide what is not available in the art, viz., a polyimide composition which exhibits a lowered dielectric constant in the range of 2.5 to 3.1 at 10 GHz.
Another object of the present invention is to provide a series of polyimides based on the dianhydride of 1,4-bis(3,4-dicarboxyphenoxy)benzene (HQDEA) that are evolved from high molecular weight polyamic acid solutions and that yield flexible free-standing films and coatings in the fully imidized form.
Another object of the present invention is to provide a series of polyimides based on 2,2-bis[4(3-aminophenoxy)phenyl]hexafluoropropane (3-BDAF) that are evolved from high molecular weight polyamic acid solutions and that yield flexible free-standing films and coatings in the fully imidized form.
Another object of the present invention is to provide a polyimide based on the HQDEA dianhydride and 3-BDAF diamine.
Another object of the present invention is to provide a polyimide composition based on HQDEA which exhibits a lowered dielectric constant, compared to the state-of-the-art commercial polyimides, in the range of 2.5 to 3.1 at 10 GHz.
Another object of the present invention is to provide a polyimide composition which exhibits a lowered dielectric constant, compared to the state-of-the-art commercial polyimides, in the range of 2.5 to 3.1 at 10 GHz.
Another object of the present invention is to make films or coatings materials from polymers based on HQDEA and/or 3-BDAF.